Following a keynote from T-Mobile’s Chief Technology Officer Neville Ray at the NGMN conference this morning, Senior Vice President of Technology Dave Mayo provided an update today regarding the company’s $4 billion 4G-network plan.

We already knew T-Mobile would be make its 4G HSPA+ in the 1900 MHz band available to iPhone users later this year as its new network equipment gets installed. It recently confirmed that it began testing the network on a small scale. Today, we get an update on the progress of the carrier’s 4G rollout with Mayo confirming installations of new equipment at the first 400 modernized GSM / HSPA+ sites, which will be complete by the end of June, with the number growing to 2,500 sites a month after. He also noted the carrier was approved for 19,500 additional sites. This indicates the LTE network is on track for its 2013 rollout.

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Mayo confirmed iPhone users can expect “more of these speed sightings will occur” as the carrier prepares to introduce its 4G HSPA+ service in the 1900 MHz spectrum “in a large number of markets later this year.” He also said next-generation Release-10 equipment will be used in its LTE trials this summer.